Code:

//------------------------------------------------------------------------------
//
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
//
// Description:
// SafeRightsManagementHandle class
//
// History:
// 10/12/2005: SarjanaS: Initial implementation.
//
//-----------------------------------------------------------------------------
using System;
using System.Runtime.InteropServices;
using Microsoft.Win32.SafeHandles;
using System.Security;
namespace MS.Internal.Security.RightsManagement
{
[SecurityCritical(SecurityCriticalScope.Everything)]
internal sealed class SafeRightsManagementHandle : SafeHandle
{
//Although it is not obvious this constructor is being called by the interop services
// it throws exceptions without it
private SafeRightsManagementHandle()
: base(IntPtr.Zero, true)
{
}
// We have incompatibility between SafeHandle class hierarchy and the unmanaged
// DRM SDK declarations. In the safe handle hierarchy it is assumed that the type
// of handle is the IntPtr (64 or 32 bit depending on the platform). In the unmanaged
// SDK C++ unsigned long type is used, which is 32 bit regardless of the platform.
// We have decided the safest thing would be to still use the SafeHandle classes
// and subclasses and cast variable back and force under assumption that IntPtr
// is at least as big as unsigned long (in the managed code we generally use uint
// declaration for that)
internal SafeRightsManagementHandle(uint handle)
: base((IntPtr)handle, true) // "true" means "owns the handle"
{
}
// base class expects us to override this method with the handle specific release code
protected override bool ReleaseHandle()
{
int z = 0;
if (!IsInvalid)
{
// we can not use safe handle in the DrmClose... function
// as the SafeHandle implementation marks this instance as an invalid by the time
// ReleaseHandle is called. After that marshalling code doesn't let the current instance
// of the Safe*Handle sub-class to cross managed/unmanaged boundary.
z = SafeNativeMethods.DRMCloseHandle((uint)this.handle);
#if DEBUG
Errors.ThrowOnErrorCode(z);
#endif
// This member might be called twice(depending on the client app). In order to
// prevent Unmanaged RM SDK from returning an error (Handle is already closed)
// we need to mark our handle as invalid after successful close call
base.SetHandle(IntPtr.Zero);
}
return (z>=0);
}
// apparently there is no existing implementation that treats Zero and only Zero as an invalid value
// so we are sub-classing the base class and we need to override the IsInvalid property along with
// ReleaseHandle implementation
public override bool IsInvalid
{
get
{
return this.handle.Equals(IntPtr.Zero);
}
}
internal static SafeRightsManagementHandle InvalidHandle
{
get
{
return _invalidHandle;
}
}
private static readonly SafeRightsManagementHandle _invalidHandle = new SafeRightsManagementHandle(0);
}
}
// File provided for Reference Use Only by Microsoft Corporation (c) 2007.